[Qgis-developer] QWC and WMS FILTER in qgis mapserver

Alessandro Pasotti apasotti at gmail.com
Thu Jan 9 09:00:51 PST 2014

2014/1/9 Marco Hugentobler <marco.hugentobler at sourcepole.ch>

>  >I thought this OGC filtering stuff was already implemented for WFS
> server isn't it?
> Yes, that's what I meant with data provider filtering vs. QGIS filtering.
> WFS server uses QgsExpression (QGIS side filtering) while WMS takes the
> filter and sets the subset to the provider (db side filtering).
> So it could be done by switching to QgsExpression depending on the filter
> format (pull requests welcome). Data provider syntax still needs to be
> supported because this kind of filtering is more powerfull and more
> performant.
> Regards,
> Marco
> On 09.01.2014 17:41, Alessandro Pasotti wrote:
>  2014/1/9 Marco Hugentobler <marco.hugentobler at sourcepole.ch>
>>  Hi Alessandro
>> >Since OGC FILTER parsing is already implemented in QGIS, would it be
>> possible make the WMS understand OGG FILTER encoding in addition to the
>> custom syntax?
>>  The problem is that the filter has the subset syntax of the data
>> provider. So it would need translation OGC syntax -> provider syntax (or
>> the possibility to choose between db server side filtering or QGIS side
>> filtering with unified syntax).
>  I thought this OGC filtering stuff was already implemented for WFS
> server isn't it?
>  --
> Alessandro Pasotti
> w3:   www.itopen.it
Ok, summarizing:

in WFS we have the standard OGC "FILTER" plus the  QGIS custom "EXP_FILTER"
in WMS we have QGIS custom "FILTER"

IMHO the best solution would be to have the same parameters also in WMS, so:

rename WMS QGIS custom  "FILTER" to "EXP_FILTER" and
implement OGC  "FILTER" even if it's not in the standard

Do you think that we can re-use the WFS OGC FILTER code for the WMS OGC
FILTER implementation?

Alessandro Pasotti
w3:   www.itopen.it
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